a) Field of the Invention
The present invention relates to a semiconductor device adapted for a high density wiring, and more particularly to a semiconductor device having contact portions on a semiconductor chip for connecting directly with a circuit board.
b) Description of the Related Art
In general, a multiplicity of integrated circuits are simultaneously manufactured on a semiconductor wafer. When the manufacturing process is finished, the wafer is severed into semiconductor chips corresponding to respective integrated circuits (IC). Each of the semiconductor chips is accommodated in a package that generally is concurrently a container and a wiring board. Bonding pads on the chip are connected with leads of the package. The package is sealed after having been wire-bonded. When the package is made of plastics, the chip is mounted on a lead frame, wire bonded, and molded with plastics such as epoxy resin, or the like. A semiconductor package thus manufactured is mounted on a printed circuit board.
A package facilitates the following objects:
1. for protecting a semiconductor chip from environmental influence chemically, electrically, and mechanically; PA0 2. for radiating heat generated from the semiconductor chip; and PA0 3. for affording an easy connection with various circuit boards by expanding fine wiring pitch of the semiconductor chip.
FIG. 10 is a sectional view showing the packaged state of a semiconductor chip in a plastic package. As shown in the figure, a semiconductor chip 1 is mounted on a die of a lead frame 52 made of 42-alloy or the like. Electrodes or bonding pads of the semiconductor chip 1 and lead portions of the lead frame 52 are wire bonded by metal wires 53 made of Au or the like. The semiconductor chip 1, the lead frame 52, and the bonding wires 53 are molded and sealed by a resin 54 such as epoxy, polyimide, etc., and form an IC package PC. When a lead frame train including a multiplicity of connected units 52 is employed, mold sealing of a multiple of chips can be performed simultaneously. Thus, cost of production can be reduced. It is suitable for mass production.
Aside from the method of wiring an IC chip by packaging described above, there is another method for wiring a semiconductor chip in a bare state. FIG. 11 is a sectional view showing a semiconductor device connection by flip-chip bonding that is one of such methods. Flip-chip bonding is a kind of wireless bonding that bonds without using any metal wire 53. In FIG. 11, metal bumps 55 made of solder or the like are formed on electrode pads on a semiconductor chip 1. The bumps 55 are directly connected with patterned conductors 56 on a printed board PCB. In such method of connection, occupied area per unit IC is almost equal to dimensions of a semiconductor chip 1. Thus, miniaturization of the circuit board compared to connection with a packaged IC is attained.
In a semiconductor device as shown in FIG. 10, an area that a package PG occupies on a printed circuit board (PCB) becomes large, so that miniaturization and increasing wiring density of the circuit board is limited. In a circuit board using flip chip bonding, metal bumps 55 of a semiconductor chip 1 are connected by directly pressing to conductive patterns, so that the semiconductor chip 1, once connected, is not easily removed. Thus, when the semiconductor chip 1 is revealed to have a deflect, exchange off the IC chip is not easy.